The techniques employed in the project have been chronic cannulation of the cisterna magna in cats used for repeated withdrawal of cerebrospinal fluid (CSF) in sleeping and waking cats, ablation of a brain hemisphere in cats during slow-wave sleep (SWS) and wakefulness and using the push-pull cannula in a specific brain structure of cats during wakefulness. We measured 5-hydroxyindoleacetic acid (5-HIAA), a 5-hydroxytryptamine (5-HT) metabolite, and homovanillic acid (HVA), a dopamine (DA) metabolite, concentrations in CSF and found that 5-HIAA concentration was significantly increased during SWS. In the brain tissue, we found 5-HT and 5-HIAA, DA and HVA significantly increased in hippocampus during SWS and DA and HVA significantly increased in thalamus-striatum during wakefulness. These findings support the implicated role of 5-HT in SWS. To examine further the activity of monoaminergic system in the brain, we will determine the concentrations of monoamines and their metabolites from selected brain regions using the push-pull cannula system of Gaddum. This approach will permit us to follow the time course of changes in brain monoamines during sleep and wakefulness and establish their differential roles during different stages of sleep. Sleep induced by hypnotic agents differs from physiological sleep. Action of hypnotics may be similar to the mechanism that regulates physiological sleep or may have a different course. While there is evidence that implicates monoamines in sleep, little has been done to elucidate interrelationship of monoamines and hypnotics. With the help of the above mentioned techniques, we are planning to obtain that information. BIBLIOGRAPHIC REFERENCES: Buckingham, R.L. and Radulovacki, M. (1975), 5-Hydroxyindoleacetic acid in cerebrospinal fluid: An indicator of slow-wave sleep. Brain Research 99:2, 440-443. Buckingham, R.L. and Radulovacki, M. (1975), The selective effects of alpha-methyl aromatic amino acids on brain monoamine metabolites and behavior in cats. Res. Com. Chem. Pathol. Pharmacol. 12:2, 255-265.